The present invention relates to techniques for assessing cancer treatment and in particular for a computerized assessment system using PET/CT or other anatomical, functional and molecular imaging techniques.
The assessment of treatment response in cancer patients receiving therapy is essential for disease management and clinical evaluation of therapy. Computed tomography (CT) is widely used to monitor cancer treatment by measuring changes in the diameters of the particular tumor lesions, for example, under the RECIST (Response Evaluation Criteria in Solid Tumors) guidelines. Such evaluations are subject to errors associated with the simplified characterization of a single dimension of a tumor, measurement of small tumors, or measurement of tumor size when tumor tissue is replaced with necrotic or fibrotic tissue. Often a particular tumor will not be representative of the disease as a whole. For these reasons, correlation between and similar measurements and clinical outcome is often weak.
Improved assessment of the efficacy of cancer treatments may be obtained by metabolic imaging of a type that can distinguish between necrotic and fibrotic tissue or healthy tissue and tumor tissue. One such imaging system is positron emission tomography (PET) that can distinguish among different types of tissue based on different uptake of a radioactive tracer compound targeted to a tumor. PET imaging may be used instead of or in addition to CT imaging to characterize particular tumors during treatment with improved result. The tumors visualized by PET may be manually identified, for example, by a physician drawing a region of interest (ROI) around the tumor and then measuring dimensions of the active portions of the tumor identified by the PET imaging
The present inventors have demonstrated a significant improvement over conventional methods by using advanced PET-based analysis for early assessment of leukemia treatment efficacy. In this system bone marrow is automatically isolated from the combined PET/CT dataset and evaluated, in one example, based on standardized uptake values (SUV). The cortical bone surrounding the bone marrow tissue provides a sharp CT contrast with the neighboring tissue; its segmentation from the rest of the body helps isolating bone marrow tissue using a simple SUV threshold on the PET image (using 3′-Deoxy-3′-[18F] Fluorothymidine (FLT) radiotracer). Measurement of bone marrow activity alone or in pre-treatment and post-treatment comparisons, as isolated from other tissue of the body, provides improved sensitivity and thus insight into the progress of the treatment.
PET-based assessment of cancer treatment treatments largely concentrate on cancers involving solid tumors . . . . Such situations of localized disease allow ready characterization of the growth or shrinkage of disease tumors. Systemic diseases such as leukemia, lymphoma, or metastatic diseases in contrast, often present a diffuse or non-localized “continuous lesions” distributed in a large volume of body tissue. Focused measurement of such continuous lesions isolated from other tissue is difficult.